She's the Brisbane grandmother who has taken her fight against a multinational biotechnology company to the highest court in the land.

Yvonne D'Arcy, 69, of Logan, near Brisbane, went to the High Court on Tuesday for the latest chapter in her David and Goliath struggle with medical diagnostics firm Myriad Genetics.

Yvonne D'arcy says no company should be able to patent genetic material.Credit:Peter Rae

When she attended her first hearing in the case five years ago, in the Federal Court in Sydney, she wore a wig to hide her hair loss from chemotherapy for a second bout of breast cancer.

On Tuesday, she came to Canberra with a healthy head of hair, having gone five years without treatment. On Friday, she will have a mammogram to determine whether she remains cancer free.

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Ms D'Arcy came to Canberra to challenge a patent covering the use of genetic mutations in diagnosing a predisposition to breast and ovarian cancer.

She says no company should be able to patent genetic material, and she fears if the patent stands, ordinary people will not be able to afford genetic testing.

"They say when it's taken out of me, it's theirs. No, it's still me. It's my genetic footprint. It's part of who I am," Ms D'Arcy told Fairfax Media.

"It doesn't belong to anyone else - it's me. And you can't own a piece of me."

The case hinges on whether the nucleic acids covered by the patent are naturally occurring, or whether the extraction of the nucleic acids from cells amounted to a "manner of manufacture."

Last year, the Full Court of the Federal Court found that the nucleic acids covered by the patent were different from those which occurred in nature, because only once they had been isolated from other materials could they be used for the purpose of testing.

On Tuesday, Ms D'Arcy's counsel, David Catterns QC, told the court that "merely to isolate a person's naturally occurring blood... does not constitute a manufacture."

Unlike actress Angelina Jolie, who had both her ovaries and both her breasts removed after learning she carried the so-called BRCA mutation, Ms D'Arcy does not possess the genetic sequence in question, but agreed to have the case run in her name by law firm Maurice Blackburn.

"I've had breast cancer twice, and I know what you go through once it's discovered and it's gone rogue," Ms D'Arcy said.

She said she hoped affordable access to genetic testing might allow other women to discover their predisposition to cancer early, take preventive action and be spared the "terrible" experience of chemotherapy and radiotherapy.

"I'm doing this for all those people who said to me 'we don't have a voice - can you be our voice?' - I'm speaking up for them."